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Chain

Chemical

Emotional

Hill

Light

Nuclear

Physical reaction - Defined by Newton's third law: "For every action there is an equal and opposite reaction". The idea that any given force has a pair or opposite force.

Reflexive

Political - The reaction is the attitude of the reactionaries, or their political movement

Risk management - The reaction is a response after the hazard. Prevention is a response before the hazard materialization.

see also Adverse drug reaction